This invention relates to superconducting devices and particularly to persistence switches for effecting transitions between persistent and non-persistent modes for superconducting circuits.
Transitions between persistent and non-persistent (driven) mode for a superconducting circuit are controlled by a persistence switch. Such a device is ordinarily known in the art to comprise a four terminal switching means akin to a monostable relay. In a common form of prior art persistence switch, a signal is supplied to two (input) terminals to drive a resistive heating element. The heat evolved thereby destroys the superconductive state of a superconducting wire which wire forms the remaining two (output) terminals of the switch. When the heating element is de-energized, the liquid helium within the cryostat quickly cools the superconducting wire below the transition point thereby re-establishing the superconductive state.
The input signals for a persistence switch communicate over conductors between the interior and exterior of the cryostat thereby forming a thermal path to the interior of the cryostat with deleterious effects upon the boil-off rate of the coolant therein (liquid helium). Even though such conductors are removed, additional heat losses are engendered by the conduit through which such conductors are introduced. In one method for reducing this contribution to the boil-off rate, the number of control conductors serving a plurality of p persistence switches is minimized by arrangement of such persistence switches in a communicating array. Each persistence switch in the array incorporates a diode in series with the switch heating element. A steering network is thereby achieved whereby any desired one of the persistence switches may be selected by exciting an appropriate pair of signal conductors leading from the exterior of the cryostat. This forms the subject matter of co-pending U.S. Pat. application Ser. No. 879,293 assigned to the assignee of the present invention.
In the present invention the heat evolved by a diode is employed to destroy the superconducting state of a superconducting wire in thermal contact therewith. No separate heating element is employed.
The object of the present invention is a novel persistence switch for use with an arrangement of similar such switches.
One feature of the present invention is a persistence switch having the characteristics of a diode whereby networks formed by a plurality p of such switches may be accommodated with a number n of actuating signal conductors such that n is less than p.
Another feature of the present invention is the utilization of the heat evolved by a forward biased diode to effect transitions in the superconducting state of a superconductor in thermal contact therewith.
Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings.